WO2008062993A1

WO2008062993A1 - Induction heating bonding apparatus

Info

Publication number: WO2008062993A1
Application number: PCT/KR2007/005842
Authority: WO
Inventors: Ki Seok Choi
Original assignee: Smart Corporation Co., Ltd.
Priority date: 2006-11-22
Filing date: 2007-11-21
Publication date: 2008-05-29
Also published as: KR100734922B1

Abstract

The invention includes a rectifier 10, a switching part 20 to generate the high frequency current, a pulse with modulator 30 to generate driving signal for switching operation, a controller 40 to control the pulse with modulator 30, a coil unit 50 to generate magnetic field to bond the materials 3. The controller 40 firstly controls the pulse width modulator 30 to generate a driving signal with the first duty ratio to raise the temperature to a target temperature, and then a reduced second duty ratio to keep the temperature of the electro-conductive member 2 at the target temperature.

Description

INDUCTION HEATING BONDING APPARATUS

Technical Field

[1] The invention relates to an induction heating bonding apparatus, and more particularly to an induction heating bonding apparatus enable to raise the temperature to a target level and keep the temperature constant to achieve uniform and high quality bonding.

[2]

Background Art

[3] Currently, the electromagnetic induction heating type bonding apparatus (hereinafter referred as "induction heating bonding apparatus") are widely used for building construction such as tile bonding, wood panel bonding, water proofing and so on. The inventions about the induction heating bonding apparatus are disclosed in Japanese patent laid-open No.2005-19374 and Korean patent application No.2005-7014370.

[4] The induction heating bonding apparatus comprises a high frequency generator and the coil unit generating magnetic field induced by the high frequency current. To bond the materials by using this apparatus, a bonding agent made of hot melting thermoplastic resin and a electro-conductive member are overlapped and inserted between two bonding parts. While the surface of the bonding materials being contacted on the coil of the induction heating apparatus, the high frequency current is generated to induce the magnetic field on the coil. Then the magnetic field results in the induced current in the electro-conductive member, which will generate the joule heat. Preferably, the joule heat should heat the electro-conductive member uniformly to have the uniform temperature all of the surface of the electro-conductive member in order to sufficiently melt the bonding agent. If there are temperature differences on the surface of the electro-conductive member, some part of the bonding agent may not be melt to incur a bonding failure.

[5] Figure 1 show the temperature variation of the electro-conductive member heated by the conventional induction heater. The temperature of the conventional induction heater is regulated by the on-off switch. That is, firstly 100% duty ratio pulse frequency with the maximum power is applied to reach a target temperature, then the power is switched off. But, these type of induction heating bonding apparatus have some problems as belows.

[6]

Disclosure of Invention Technical Problem [7] Generally the thickness of the electro-conductive member is not uniform. So, if the power is switched off, the thin part of the member is sufficiently heated to have high temperature, but the thick part of it is not sufficiently heated to have low temperature relatively, which will result in bonding failure. If we are to heat the thick part sufficiently, then the thin part will be overheated and damaged.

[8] We may consider to adopt current sensor to detect the current on the electro- conductive member and control the current constantly by way of the feed back control in order to keep the heat uniform. But so many sensors are needed and the overall structure may become complicated because attaching and wiring of the sensors are not easy.

[9] In addition, as the induction heating bonding is used on various fields, and the required electrical properties and dimensions of the induction heating device are different to each other. Therefore, various types of induction heating bonding apparatus having different electrical properties and dimensions should be prepared.

[10]

Technical Solution

[11] The invention is suggested to solve the above mentioned problems, and the object of the invention is to provide a new induction heating bonding apparatus enable to bond the materials uniformly with the uniform temperature all over the bonding surface of the electro-conductive member without bonding failure or material damage.

[12] Another object of the invention is to provide a new induction heating apparatus enable to bond various kind and different size materials with a single bonding apparatus.

[13] And, another object of the invention is to provide a new induction heating apparatus enable to increase the bonding strength and reduce the required bonding time by cooling the temperature rapidly after the electro-conductive member reaches a target temperature.

[14]

[15] According to one aspect of the invention, there is provided an induction heating bonding apparatus, which includes a rectifier 10 converting AC into DC, a switching part 20 connected to the rectifier 10 and receiving the DC and generating the high frequency current, a pulse with modulator 30 connected to the switching part 20 to generate driving signal for switching operation, a controller 40 connected to the input of the pulse width modulator 30 to control the pulse width modulator 30, a coil unit 50 connected to the switching part 20 to generate magnetic field to cause the induced current on the electro-conductive member 2 adjacent to bonding materials 3 to bond the bonding materials 3 by generating the joule heat, wherein the controller 40 firstly controls the pulse width modulator 30 to generate a driving signal with the first duty ratio to raise the temperature of the electro-conductive member 2 to a target temperature, and then controls the pulse width modulator 30 to generate a driving signal with a reduced second duty ratio to keep the temperature of the electro- conductive member 2 at the target temperature.

[16]

[17] According to anther aspect of the invention, there is provided an induction heating bonding apparatus, wherein the controller 40 has a memory 60 storing the values of temperature rising time, temperature keeping time, and the corresponding duty ratio during each time, and a interface panel 70 to display, select or adjust the values of times and duty ratios.

[18]

[19] According to another aspect of the invention, there is provided an induction heating bonding apparatus, wherein the coil unit 50 includes a plurality of coils 51 according to the type and dimension of the bonding materials, and a coil selector 80 is provided between the coil unit 50 and the switching part 20 and connected to the controller 40 to select one of the coils 51 through the interface panel 70.

[20]

[21] According to another aspect of the invention, there is provided an induction heating bonding apparatus, wherein a cooling unit 90 is further provided to be controlled by the controller 40 to cool the coil unit 50 and the controller 40 can control to start the cooling unit 90 when the high frequency current from the coil unit 50 stops.

[22]

Advantageous Effects

[23] According to the invention as described above, as the controller 40 could control the pulse width modulator 30 to generate the driving signal with the maximum of the first duty ratio to raise the temperature of the electro-conductive member 2 to a target temperature and then generate the driving signal with the reduced duty ratio to keep the temperature of the electro-conductive member 2 at the target temperature, the overall surface of the electro-conductive member 2 could be uniformly heated without any temperature difference to melt the bonding agent uniformly and sufficiently so the bonding failure or poor bonding could be avoided. And, as the data of duty ratios of driving signal according to the bonding conditions such as the bonding material 3, the bonding agent 1 or the electro-conductive member 2 are stored in the memory 60 beforehand and the data can be displayed, selected or adjusted through the interface panel 70, the bonding material could be heated at the optimal condition based on the predetermined values easily to achieve a high quality bonding. [24] Moreover, the coil unit 50 comprises a plurality of coil 51, which could be selected by a coil selector 80, therefore it could be possible to meet the needs of bonding in the various fields with a single bonding apparatus. In addition, as the cooling unit 90 controlled by the controller 40 could cool the coil unit 50 down to the room temperature when the heating of the electro-conductive member 2 stops, the time required to bonding operation could be reduced, and the bonding strength could be increased. And, as any sensor to detect the temperature of the electro-conductive member 2 for feed back control is not necessary, the structure of the bonding apparatus could be simple and bonding quality may be improved without bonding failure.

[25]

Brief Description of the Drawings

[26] Figure 1 is a graph showing the temperature variation of the electro-conductive member heated by the induction heating apparatus.

[27] Figure 2 is a block diagram of the circuitry of the invention.

[28] Figure 3 is a graph showing the temperature variation of the electro-conductive member according to the invention.

[29] Figure 4 is graph showing the temperature variation of the electro-conductive member according to the duty ration values.

[30]

Best Mode for Carrying Out the Invention

[31] The preferred embodiment of the invention will be described with reference to the accompanied drawings.

[32] Figure 2 shows the circuitry of the induction heating bonding apparatus according to the invention. As shown, the invention includes rectifier 10 receiving the commercial AC and outputting the DC, a switching part 20 connected to the rectifier 10 and switching it to generate the high frequency current, a pulse width modulator 30 connected to the switching part 20 to generate driving signal for switching operation, a controller 40 connected to the input of the pulse width modulator 30 to control the pulse with modulator 30, a coil unit 50 connected to the switching part 20 to generate magnetic field to bond the materials 3 by generating the joule heat caused by the induced current on the electro-conductive member 2 adjacent to bonding materials 2.

[33] The rectifier 10 comprises of AC line filter 11, a full wave rectifying circuit 12 and a high frequency filter 13. The line filter 11 filters the noise flowing through the power line. The full wave rectifying circuit 12 converts AC into DC and supplies it to switching part 20. The high frequency filter 13 passes the high frequency current and blocks the low frequency current.

[34] The switching part 20 is preferably made of a IGBT switching element with a high switching property for the high speed switching operation.

[35] The controller 40 applies a necessary control signal to the switching part 20 for the high speed switching. The control signal enables the pulse width modulator 30 connected to the controller 40 to generate a driving signal of certain duty ratio to the switching part 20.

[36] The switching part 20 driven by the pulse width modulator 30 conducts a switching operation to modulate the high frequency current from the rectifier 10, and the PWM controlled high frequency current is applied to the coil unit 50. As the coil unit 50 is positioned near to the electro-conductive member 2, the magnetic field generated by the coil unit 50 should induce the current in the electro-conductive member 2, which in turn generates the joule heat in the electro-conductive member 2. The joule heat may raise the temperature of the electro-conductive member 2 to a predetermined target temperature.

[37] Figure 3 is a graph of the temperature variation of the electro-conductive member 2 according to the invention and shows the relation of time and temperature according to the duty ratio of the driving signal. As shown, during the first predetermined time, the first duty ratio which is maximum ratio is applied to the coil unit 50, and after that, the second duty ratio with a reduced value is applied to the coil unit 50 for the predetermined time. As the driving signal of the reduced duty ratio is applied to the coil unit 50, the output power of the high frequency current of the coil unit 50 is also reduced, so the temperature of the electro-conductive member 2 may not rise and be kept constant.

[38] The data of the temperature rising time, the temperature keeping time and the corresponding duty ratios according to the type of bonding materials and the electro- conductive members are stored on the memory 60. And the interface panel 70 is further provided to display, select or adjust the value of the predetermined time and duty ration according to the bonding materials and the electro-conductive members.

[39] Figure 4 shows the temperature variation of the electro-conductive member according to the duty ratio values. The second duty ratio stored in memory 60 for the temperature keeping time is determined as the range from 18% to 25%. And the temperature rising time of duty ratio 100% is determined as the range from 0.8 sec to 1.9 sec. The temperature keeping time could be determined as same for all case. For example, it could be 5 sec. The values of the time could be determined according to the thickness and type of the bonding agent, the bonding materials (material to be bonded), and the electro-conductive member.

[40] The interface panel 70 includes the display 71 to display the values and the key button 72 to input, select or adjust the values. For example, the second duty ratio can be adjusted to raise each step of 1% from 15% to 25%, and the temperature rising time for the first duty ratio could be adjusted stepwise from 0.8 sec to 3 sec.

[41] The coil unit 50 comprises of a plurality of coil 51 with the different shape or property according to the type of dimension of the bonding materials. And a coil selector 80 is provided between the coil unit 50 and the switching part 20 and controlled by the controller 40 to select the coil 51 of the coil unit 50 for which the high frequency current is applied according to the bonding materials.

[42] A cooling unit 90 is connected to the controller 40 to cool the coil unit 50 according to the control of the controller 40. When the controller 40 detects that the high frequency current to the coil unit 50 is switched off, then generates the instruction to start the cooling unit 90. Figure 4 describes the temperature down curve according to the invention, which shows that the temperature of the electro-conductive member 2 and bonding agent 1 being rapidly down by the cooling unit 90 in contrast to the conventional art. This cooling unit 90 is advantageous to reduce the bonding time and increase the bonding strength.

[43] The element of numeral 99 is a cooler to cool down the switching part 20.

[44] The foregoing embodiment do not limit the scope if the disclosed invention. For example, the high frequency filer 13 is described as a part of the rectifier 10, it may be designed not to be a part of the rectifier 10. And the coil unit 50 can heat the stationary bonding materials or some part of the bonding materials. And, the coil unit 50 may be movable to heat the stationary bonding materials, or the stationary coil unit 50 can heat the movable bonding materials. Therefore, the induction heating bonding apparatus of the invention could be used for various fields such as sheet bonding such as a water proofing sheet, a wood bonding for furniture, a cup sealer and so on.

[45]

Claims

[1] An induction heating bonding apparatus, which includes a rectifier 10 converting

AC into DC, a switching part 20 connected to the rectifier 10 and receiving the DC and generating the high frequency current, a pulse with modulator 30 connected to the switching part 20 to generate driving signal for switching operation, a controller 40 connected to the input of the pulse width modulator 30 to control the pulse width modulator 30, a coil unit 50 connected to the switching part 20 to generate magnetic field to cause the induced current on the electro- conductive member 2 adjacent to bonding materials 3 to bond the bonding materials 3 by generating the joule heat, wherein the controller 40 firstly controls the pulse width modulator 30 to generate a driving signal with the first duty ratio to raise the temperature of the electro-conductive member 2 to a target temperature, and then controls the pulse width modulator 30 to generate a driving signal with a reduced second duty ratio to keep the temperature of the electro- conductive member 2 at the target temperature.

[2] An induction heating bonding apparatus of claim 1, wherein the controller 40 has a memory 60 storing the values of temperature rising time, temperature keeping time, and the corresponding duty ratio during each time, and a interface panel 70 to display, select or adjust the values of times and duty ratios.

[3] An induction heating bonding apparatus of claim 1 or 2, wherein the coil unit 50 includes a plurality of coils 51 according to the type and dimension of the bonding materials, and a coil selector 80 is provided between the coil unit 50 and the switching part 20 and connected to the controller 40 to select one of the coils 51 through the interface panel 70.

[4] An induction heating bonding apparatus of claim 1 or 2, wherein a cooling unit

90 is further provided to be controlled by the controller 40 to cool the coil unit 50 and the controller 40 can control to start the cooling unit 90 when the high frequency current from the coil unit 50 stops.